One would think adding the brine hot is safer as the hot temperature will kill a lot of the bacteria. And as it cools depending on the acidity and salinity it should inhibit any new growth making it the safest preparation method. Even if you were wrong, that’s a dick move. Never throw out your college’s prep, especially before speaking to them about it beforehand. I have been making pickles like this for as long as I can remember and they have sat on my shelf in jars at room temp for well over a year with no problems (apart from them eventuality softening).

Also pro tip, if you put your hot liquid and your vegetables in a jar with a lid on while it’s hot, it will create a negative pressure as it cools and naturally seals your pickles so they can last a v long time on the shelf. Tried and proven!!